﻿using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Text.RegularExpressions;
using System.IO;

namespace ProjectEulerSolutions
{
    /*
     * By starting at the top of the triangle below and moving to adjacent numbers on the row below, the maximum total from top to bottom is 23.

3
7 4
2 4 6
8 5 9 3

That is, 3 + 7 + 4 + 9 = 23.

Find the maximum total from top to bottom of the triangle below:

75
95 64
17 47 82
18 35 87 10
20 04 82 47 65
19 01 23 75 03 34
88 02 77 73 07 63 67
99 65 04 28 06 16 70 92
41 41 26 56 83 40 80 70 33
41 48 72 33 47 32 37 16 94 29
53 71 44 65 25 43 91 52 97 51 14
70 11 33 28 77 73 17 78 39 68 17 57
91 71 52 38 17 14 91 43 58 50 27 29 48
63 66 04 68 89 53 67 30 73 16 69 87 40 31
04 62 98 27 23 09 70 98 73 93 38 53 60 04 23

NOTE: As there are only 16384 routes, it is possible to solve this problem by trying every route. However, Problem 67, is the same challenge with a triangle containing one-hundred rows; it cannot be solved by brute force, and requires a clever method! ;o)

     * 
     * 
     * */
    class Problem18
    {
        public static string Calculate()
        {
            string input;
            using (StreamReader sr = new StreamReader("Problem18.txt"))
            {
                input = sr.ReadToEnd();
            }

            var matches = Regex.Matches(input, "[0-9]+").Cast<Match>()
                .Select(xv => xv.Value).ToList();


            int x = 0;
            int y = 1;

            long[] sums = new long[matches.Count];

            sums[0] = int.Parse(matches[0]);

            for (int i = 1; i < matches.Count; i++)
            {
                if (x == 0) //-y
                {
                    sums[i] = int.Parse(matches[i]) + sums[i - y];
                }
                else if (x == y) //-y-1
                {
                    sums[i] = int.Parse(matches[i]) + sums[i - y - 1];
                }
                else //oboje
                {
                    //vecu ili svejedno
                    sums[i] = int.Parse(matches[i]) + (sums[i - y - 1] > sums[i - y] ? sums[i - y - 1] : sums[i - y]);
                }

                x++;
                if (x > y)
                {
                    y++;
                    x = 0;
                }
            }

            long max = 0;
            for (int i = sums.Length - 1 - y - 1; i < sums.Length; i++)
            {
                if (sums[i] > max)
                    max = sums[i];
            }

            return max.ToString();
        }


    }
}
